1. Field of the Invention
The present invention relates generally to telecommunications systems and methods for generating alarms due to base station failure, and specifically to providing a cell traffic supervision alarm.
2. Background and Objects of the Present Invention
Mobile communications, especially cellular radio, is one of the fastest growing and most demanding telecommunications applications ever. Today it accommodates a large and continuously increasing percentage of all new telephone subscriptions around the world with the increasing service requirements. Cellular networks have evolved into two different networks within Time Division Multiple Access (TDMA) technology. The European cellular network uses the Global System for Mobile Communication (GSM) standard as the digital cellular system. In the United States, cellular networks have traditionally been primarily analog, but recent advances have been incorporating digital systems within the analog networks. One such North American cellular network is the D-AMPS network, which is described hereinbelow.
With reference now to FIG. 1 of the drawings, there is illustrated a D-AMPS Public Land Mobile Network (PLMN), such as cellular network 10, which in turn is composed of a plurality of areas 12, each with a Mobile Switching Center (MSC) 14 and an integrated Visitor Location Register (VLR) 16 therein. The MSC/VLR areas 12, in turn, include a plurality of Location Areas (LA) 18, which are defined as that part of a given MSC/VLR area 12 in which a mobile station (MS) 20 may move freely without having to send update location information to the MSC/VLR area 12 that controls the LA 18.
Each Location Area 12 is divided into a number of cells 22. Mobile Station (MS) 20 is the physical equipment, e.g., a car phone or other portable phone, used by mobile subscribers to communicate with the cellular network 10, each other, and users outside the subscribed network, both wireline and wireless. The MSC 14 is in communication with a Base Station (BS) 24. The BS 24 is the physical equipment, illustrated for simplicity as a radio tower, that provides radio coverage to the geographical part of the cell 22 for which it is responsible.
With further reference to FIG. 1, the PLMN Service Area or cellular network 10 includes a Home Location Register (HLR) 26, which is a database maintaining all subscriber information, e.g., user profiles, current location information, and other administrative information. The HLR 26 may be co-located with a given MSC 14, integrated with the MSC 14, or alternatively can service multiple MSCs 14, the latter of which is illustrated in FIG. 1.
The VLR 16 is a database containing information about all of the MS's 20 currently located within the MSC/VLR area 12. If an MS 20 roams into a new MSC/VLR area 12, the VLR 16 connected to that MSC 14 will request data about that MS 20 from the HLR database 26 (simultaneously informing the HLR 26 about the current location of the MS 20). Accordingly, if the user of the MS 20 then wants to make a call, the local VLR 16 will have the requisite identification information without having to reinterrogate the HLR 26. In the aforedescribed manner, the VLR and HLR databases 16 and 26, respectively, contain various subscriber information associated with a given MS 20.
If a failure occurs in a BS 24, in many cases, the BS 24 will be unable to handle any traffic. Loss of service at a cell 22 means a loss of revenue to the network operator as well as an inability by mobile subscribers to place calls. The inability of mobile subscribers to place calls can cause dire consequences, especially if one or more of the calls is an emergency call.
Currently, there are specially-designed alarms in place in BS's 24 to detect specific hardware or software conditions. However, there are certain conditions under which a BS 24 will be unable to handle any traffic, but yet there is no alarm transmitted to the MSC 14. Causes for this may include, but are not limited to, normal degeneration or vandalism of certain key cables inside the BS 24 which may not have alarm supervision. In this situation, routine checks of the BS 24 might uncover the problem, or an operator at the MSC 14 might notice that there has been no traffic on the BS 24 for an unreasonable period of time. However, especially in the case of remote BS's 24, such routine checks may be infrequent. Alternatively, the condition might come to the attention of the operator if a user complains about lack of service.
All of the above solutions are inadequate to protect against potentially lengthy periods of time during which service in a cell 22 is unavailable, which can cause, among other things, as stated hereinbefore, increased customer dissatisfaction and loss of revenue for the operator. In addition, as mention above, loss of service even for a small period of time could also result in serious consequences if an emergency call is necessary but not possible.
It is, therefore, an object of the present invention to provide an alarm that is triggered by lack of normal traffic at a cell site.
It is a further object of the present invention that the alarm automatically adjusts itself based upon the normal traffic load at the cell site.